Commercial roasted and ground coffees are typically comprised of the two coffee types, Arabicas which are comprised f Colombian Milds and Brazilians and the Robustas which are of lesser quality. The Arabicas are characterized by good, aromatic flavor notes and the typically less expensive Robustas are characterized as having bitter and rubbery flavor notes.
With the Robustas being less expensive and contributing balancing flavor notes, it is desirable to introduce a relatively high proportion of Robustas in a commercial blend of coffees, but the characteristic strong flavor notes limit the amount of Robustas that may be added. Typically, the amount of Robustas is limited to about 35% by weight of a commercial coffee blend. It is desirable to provide a method for increasing the proportion of Robusta coffees that may be added to a typical commercial coffee blend and, at the same time, provide a coffee having increased extractability.
Roasting techniques for altering the flavor and soluble solids yield of coffee are known. For example, U.S. Pat. No. 3,088,825 to Topalian et al. teaches a roasting cycle comprising pre-heating the coffee, roasting coffee with steam under pressure and suddenly releasing the pressure. Another patent, U.S. Pat. No. 3,106,470 to Spotholz et al. discloses a similar process operating at somewhat lower steam roasting pressures. Both disclosures point out that a coffee so steamed provides a brew of higher soluble solids content upon extraction. These techniques are useful for roasting coffee, particularly Robusta coffee, but brews prepared from the roasted coffee though having higher solids content, tend to be characterized as having high acid and sour notes.
A roasting method for producing a specially processed Robusta coffee is disclosed in U.S. Pat. No. 3,640,726 to Bolt et al. The Robusta coffee is first steamed in a confined vessel preferably for between 2.5 minutes and 6 minutes. The partially roasted coffee is then held for a period of time not exceeding 2 hours and subsequently conventionally roasted. The Robusta coffee so roasted is then blended with untreated roasted Robustas as well as roasted Arabicas. Treatment of the Robustas according to this method produces a coffee which has lessened off-flavor notes but is characterized as prune-like, acid and green apple (sweet-sour).
An apparatus for the continuous roasting of coffee is disclosed in U.S. Pat. No. 3,572,235 to Nutting et al. wherein the beans are first pre-heated with steam under pressure in a confined roasting vessel, and subsequently roasted in a fluidized bed apparatus. Specifically, the fluidized bed roasting described therein is limited to charging the beans to a gas impervious plate and impinging a heated gas on said plate to fluidize said beans. A process for roasting coffee in such an apparatus is disclosed in U.S. Pat. No. 3,595,668 also to Nutting et al. The process specifically requires fluidized bed roasting of the coffee after steaming.
Another disclosure, U.S. Pat. No. 4,349,573 to Stefanucci et al., describes a method of producing a low density roasted and ground coffee product which provides 20% more brewed coffee of equal quality than a conventionally roasted and ground coffee product. The coffee is roasted for shorter times at higher temperatures in conventional coffee roasting equipment. The 20% increase in the amount of brewed coffee produced is a significant advantage but a still further increase in the brewed coffee produced from a given weight of coffee (or, a reduction in the weight of coffee used to produce the same amount of brewed coffee) is at times desirable.
It is an object of the present invention to provide a method of roasting and blending Robusta coffee whereby a higher proportion of said Robusta coffee may be added to the blend without adversely affecting the flavor of the blend.
A further object of the present invention is to provide a method of roasting Robusta coffee which coffee has lessened characteristic strong flavor notes.